Turbine for an exhaust gas turbocharger

ABSTRACT

In a turbine for exhaust gas turbocharger of a combustion engine with a turbine casing forming an installation space in which a turbine wheel is arranged so as to be rotatable about an axis of rotation and into which exhaust gas of the combustion engine may be supplied via at least one flow duct in which a guide vane structure is arranged, the guide vane structure includes vanes, which are pivotably supported relative to the turbine casing and form an axial inlet nozzle structure adjacent a wall portion of the turbine which extends along the guide vane structure, the wall portion comprising at least a first guide wall area which overlaps the guide vane structure, and which is set back relative to a second guide wall area in which the vanes are pivotably supported and which adjoins the first wall area.

This is a Continuation-in-Part application of pending internationalpatent application PCT/EP2012/002637 filed Jun. 22, 2012 and claimingthe priority of German patent application 10 2011 108 195.3 filed Jul.20, 2011.

BACKGROUND OF THE INVENTION

The present invention relates to a turbine for an exhaust gasturbocharger including a turbine casing with a turbine wheel rotatablydisposed therein and guide vanes which are adjustably supported forcontrolling the exhaust gas flow to the turbine wheel.

DE 10 2008 034 751 A1 discloses a turbocharger for a combustion enginewith a turbine casing and a turbine comprising a turbine wheel arrangedtherein, wherein the turbine is equipped with adjustable guide vanes forvarying a flow cross-section via which the exhaust gas is directed ontothe turbine wheel. A floating spacer ring is provided between theadjustable guide vanes and the turbine casing, which is in contact withthe incoming exhaust gas via a pressure duct, and the rear side of whichmay be exposed to the exhaust gas. During operation of the turbocharger,a force resultant is generated which acts axially upon the spacer ringand pushes the spacer ring against the end faces of the guide vanes bythis force resultant.

It is the object of the present invention to provide a turbine for anexhaust gas turbocharger with an improved variability or adjustability,respectively.

SUMMARY OF THE INVENTION

In a turbine for an exhaust gas turbocharger of a combustion engine witha turbine casing forming an installation space in which a turbine wheelis arranged so as to be rotatable about an axis of rotation and intowhich exhaust gas of the combustion engine may be supplied via at leastone flow duct in which a guide vane structure is arranged, the guidevane structure includes vanes, which are pivotably supported relative tothe turbine casing and form an axial inlet nozzle structure adjacent awall portion of the turbine which extends along the guide vanestructure, the wall portion comprising at least a first guide wall areawhich overlaps the guide vane structure, and which is set back relativeto a second guide wall area in which the vanes are pivotably supportedand which adjoins the first wall area.

Such a turbine for an exhaust gas turbocharger of a combustion enginecomprises a turbine casing which at least partially defines aninstallation space in which a turbine wheel may be arranged so as to berotatable about an axis of rotation relative to the turbine casing.Exhaust gas of the combustion engine may be supplied to the installationspace via at least one flow duct in which a guide vane structure isarranged which is movable relative to the turbine casing. The flow ductis defined in the axial direction of the installation space and thus ofthe turbine wheel at least partially by at least one wall portion of theturbine which is at least partially overlapping the guide vane. In otherwords, the second wall area is closer to the guide vane than the firstwall area. Therefore, the wall areas do not extend in a common plane.Rather, the wall areas extend e. g. in two different planes which arearranged in the axial direction on different levels, and which e. g. atleast essentially extend parallel to each other and/or which e. g. atleast essentially extend vertically to the axial direction.

Because of this special design of the wall portion, in particular of theouter contour facing towards the guide vane, the inventive turbineexhibits especially low friction and an improved variability oradjustability, respectively. In particular, the guide vanes may be movedwith very low friction and thus operate extremely smoothly, in order tovariably establish proper flow conditions for the exhaust gas of thecombustion engine entering the flow duct and to precisely adapt the vanepositions to different operating points of the combustion engine. Thisresults in an improved operability which keeps the fuel consumption andthe CO₂ emission of the combustion engine low.

The guide vanes are, for example, pivotable about a pivot axis relativeto the turbine casing in order to e. g. adjust a flow cross-section ofthe inlet flow duct for the exhaust gas. This means that the flowcross-section may be at least partially fluidly blocked or unblocked.

Since the first wall area is set back relative to the second wall area,the inventive turbine exhibits extremely low friction when the guidevane is at least partially opened. This is accompanied by a lowhysteresis which in turn enhances the efficient operation and a highefficiency of the turbine.

Since the first wall area is set back relative to at least the secondwall area, the inventive turbine, in particular with opened guide vane,has an extremely high absorption capacity, so that a high exhaust gasmass flow may pass the turbine. In the upper load and/or speed rangesand thus at high exhaust gas mass flow, the inventive turbine allows aparticularly efficient operation of the combustion engine and therealisation of particularly high power and/or torque values, because itpermits an extremely high exhaust gas mass flow. The turbine does notrepresent an undesired high flow resistance for the high exhaust gasmass flow, so that charge changing losses are kept particularly small.This enhances the fuel-efficient operation of the combustion engine andis accompanied by low CO₂ emission.

The inventive turbine further comprises a particularly advantageouscontrollability when installed on a combustion engine, so that thelatter can be particularly efficiently operated. Moreover, no negativeeffects on the efficiency of the turbine and the exhaust gasturbocharger in low speed and/or load ranges occur, so that theinventive turbine provides for a fuel-efficient operation of thecombustion engine almost in the entire operating range.

Another advantage of the set-back of the first wall area is that itresults in an advantageously low acceleration between the guide vane andthe turbine wheel. The inventive turbine may be employed for combustionengines in the form of gasoline engines or diesel engines, which arereciprocating engines. It may also be employed for other combustionengines which are operated e. g. with gaseous and/or liquid fuels.

In an advantageous embodiment of the invention, the wall portion withthe wall areas is arranged on the side facing the turbine wheel outletarea of the turbine of the guide vane. In other words, the flow ductthrough the wall portion with the two appropriately formed wall areas isarranged on the side facing the turbine wheel outlet area of theturbine. Thereby, the friction of the inventive turbine, in particularwith the at least partially opened guide vane, may be kept extremelylow, which in turn is beneficial for the wear of the inventive turbine.

In a particularly advantageous embodiment of the invention, the firstand second wall areas are joined via a third wall area of the wallportion, which is arranged between the first and second wall area. Thethird wall area extends at an angle of essentially 90° max, each betweenthe first and second wall area. This means that a transition areabetween the first and second wall area is formed essentiallystep-shaped. This allows advantageous flow conditions for the exhaustgas flowing through the flow duct, which brings about a particularlyhigh efficiency of the inventive turbine. At the same time, themanufacturing costs for the inventive turbine are kept low, which inturn is accompanied by low costs for the entire combustion engine.

In another particularly advantageous embodiment of the invention, thethird wall area is formed essentially arc-shaped, in particular in theradial direction of the installation space thus of the turbine wheel.This enables favourable flow conditions for the exhaust gas through theflow duct. In particular, turbulences and/or other negative effects foran efficient flow of the exhaust gas into the installation space may beavoided. This contributes to a particularly high efficiency and aparticularly efficient operation of the inventive turbine.

The appropriate design of the first and second wall area as well as, inparticular, of the third wall area disposed therebetween has to beadapted to the corresponding requirements and applications. Theinventive turbine may be employed, for example, in a combustion enginefor a passenger car as well as in a combustion engine for a commercialmotor vehicle or another motor vehicle.

In another advantageous embodiment of the invention, the first wallarea, with the turbine wheel of the turbine arranged at least partiallyin the installation space, extends at least in the radial direction ofthe installation space and thus of the turbine wheel at least to thelevel of the leading edge of a rotor blade of the turbine wheel. Theexhaust gas is conveyed to the rotor blade and thus the turbine wheelacross the leading edge, with the leading edge extending e. g. at leastessentially in the axial direction of the installation space and thus ofthe turbine wheel. By this design of the first wall area which is setback relative to the second wall area, the first wall area preferablyhas a particularly long radial extension which contributes toparticularly low friction and an advantageous operability and aparticularly advantageous operation of the inventive turbine.

Preferably, the second wall area adjoins the first wall area at least inthe radial direction of the installation space and the turbine wheel.This means that starting from the installation space towards the flowduct, at first the first wall area is provided followed by the secondwall area. This contributes to a particularly high efficiency of theinventive turbine.

In another advantageous embodiment of the invention, the wall portion isformed by a cover element, in particular a cover plate, of the turbine,which is an insert component which is formed separately from the turbinecasing is arranged at least partially in the installation space and bymeans of which at least one leading edge, in particular a blade edge ofthe rotor blade of the turbine wheel which is at least partiallyarranged in the installation space may be at least partially covered oris covered, respectively. Thereby, particularly favorable andadvantageous flow conditions for the exhaust gas flowing through theturbine and in particular through the flow duct may be realised, whichin turn enhances the efficient operation and the efficiency of theinventive turbine.

Further, the provision of the insert component enables a particularlysimple and cost-efficient manufacture and assembly of the inventiveturbine, which keeps the costs of the entire combustion engine low.

It may be provided that the guide vane is held movable, in particularpivotable, about the pivot axis, on the cover element relative to theturbine casing and the cover element. This enhances a simple andcost-efficient assembly of the inventive turbine.

Preferably, the cover element has a cover contour by means of which theleading edge, in particular the blade edge, is at least partiallycovered and which is formed at least partially as an at leastessentially corresponding complementary contour to the outer contour ofthe leading edge. Thereby, a particularly advantageous cover of theleading edge, in particular of the blade edge, may be realized. Thisgenerates particularly advantageous flow conditions for the exhaust gasflowing to and flowing off the turbine wheel or its rotor blades,respectively. Thereby, the inventive turbine exhibits a particularlyefficient operation and a particularly high efficiency, which enhancesan efficient and fuel-efficient operation of the combustion engine.

In another advantageous embodiment of the invention, the guide vanes aresupported by a retaining component which is formed separately from theturbine casing, in particular on a nozzle ring, wherein the retainingcomponent is an insert component, which is accommodated in the turbinecasing. This enables a particularly simple, time-saving andcost-efficient assembly of the inventive turbine as well as aparticularly cost-efficient manufacture.

Further advantages, features and details of the invention will becomeapparent from the following description of preferred exemplaryembodiments with reference to the accompanying drawings. The featuresand feature combinations as previously mentioned in the description aswell as the features and feature combinations which will be mentioned inthe following description of the figures and/or which are solelyillustrated in the figures are not only applicable in the respectiveindicated combination but also in other combinations or isolated,without deviating from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial cross-sectional view of part of an exhaust gasinternal combustion engine;

FIG. 2 is another and enlarged schematic longitudinal sectional viewshowing portions of the exhaust gas turbocharger according to FIG. 1;

FIG. 3 shows portions of a schematic longitudinal sectional view ofstill another embodiment of the exhaust gas turbocharger according toFIG. 2; and

FIG. 4 shows portions of a schematic longitudinal sectional view ofanother embodiment of the exhaust gas turbocharger according to FIGS. 2and 3.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows an exhaust gas turbocharger 10 for a combustion enginewhich is in the form for example of a reciprocating piston engine. Theexhaust gas turbocharger 10 comprises a turbine 12 with a turbine casing14 which houses a turbine wheel 20 and comprises a spiral duct 16through which the exhaust gas of the combustion engine is supplied tothe turbine wheel 20. The spiral duct 16 is fluidly connected with atleast one cylinder of the combustion engine so that exhaust gas from thecylinder may enter the spiral duct 16.

The turbine casing 14 also at least partially defines an installationspace 18 in which the turbine wheel 20 of the turbine 12 isaccommodated. The turbine wheel 20 is arranged in the installation space18 and rotatable about an axis of rotation 22 relative to the turbinecasing 14.

The turbine wheel 20 is part of a rotor 24 of the exhaust gasturbocharger 10, which comprises a shaft 26. The turbine wheel 20 isnon-rotatably connected to the shaft 26 which is r supported in abearing housing 28 of the exhaust gas turbocharger 10 so as to berotatable about the axis of rotation 22 relative to the turbine casing12 and the bearing housing 28. The turbine casing 14 and the bearinghousing 28 are connected to each other.

The rotor 24 also comprises a compressor wheel 30 of a compressor 32 ofthe exhaust gas turbocharger 10. The compressor wheel 30 is alsonon-rotatably connected to the shaft 26. The compressor 32 comprises acompressor casing 34 which is also securely connected to the bearinghousing 28 and by which an installation space 36 is at least partiallydefined in which the compressor wheel 30 which is supported rotatablyabout the axis of rotation 22 relative to the compressor casing 34 is atleast partially accommodated.

The exhaust gas flowing through the spiral duct 16 is guided by thespiral duct 16 to a nozzle 38 of the turbine 12, via which the exhaustgas may flow at least essentially in the radial direction to, andimpinge on, the turbine wheel 20. This is indicated in FIG. 1 by adirection arrow 40. The turbine wheel 20 comprises a hub body 42provided with a plurality of rotor blades 44. The rotor blades 44 arearranged at least essentially equally spaced about the circumference ofthe turbine wheel 20 and securely connected to the hub body 42. FIG. 1shows only one of the pluralities of rotor blades 44.

The rotor blade 44 comprises a leading edge 46 which extends at leastessentially in the axial direction, via which the turbine wheel 20 isexposed to the exhaust gas flow. The rotor blade 44 further has a bladeedge 48 and a trailing edge 50 via which the exhaust gas may flow offthe turbine wheel 20 or the rotor blade 44, respectively. In otherwords, the exhaust gas flows across the leading edge 46 onto the turbinewheel 20 or its rotor blades 44, respectively, and flows off at leastessentially past the trailing edge 50 into a turbine wheel outlet area52. The radial direction of the installation space 18 and thus of theturbine wheel 20 or of the turbine 12, respectively, is indicated inFIG. 1 by a direction arrow 54, while the axial direction is indicatedby a direction arrow 56 in FIG. 1.

By this application of the exhaust gas, the turbine wheel 20 rotatesabout the axis of rotation 22, which in turn rotates the shaft 26 aswell as the compressor wheel 30 about the axis of rotation 22. Theturbine 12 is a radial turbine and drives the compressor 32, which is aradial compressor that takes in and compresses air. The sucked-in airflows across a leading edge 58 of a compressor blade 60 of thecompressor wheel 30 and flows off across a trailing edge 62 of thecompressor blade 60. The compressed air is then guided through acompressor spiral duct 64 which is formed by the compressor casing 34 tothe at least one cylinder of the combustion engine.

As can be seen from FIG. 1, the nozzle 38 extension in the axialdirection of the turbine 12 or of the installation space 18,respectively, (direction arrow 56) at the side facing the bearinghousing 28 is delimited at least partially by a nozzle ring 66. Thenozzle ring 66 is formed as a separate insert component relative to theturbine casing 14 and accommodated in the turbine casing 14. For fixingthe nozzle ring 66 in place relative to the turbine casing 14, amounting ring 68 is provided, by which the nozzle ring 66 is retained.The mounting ring 68 is arranged in the axial direction between theturbine casing 14 and the bearing housing 28 and clamped between them.In this manner, the nozzle ring 66 may be indirectly supported by theturbine casing 14 via the mounting ring 68 in a spaced relationship toturbine casing 14 and secured relative thereto.

At the side facing the turbine wheel outlet area 52, the nozzle 38 is atleast partially defined by a cover plate 70. The cover plate 70 is inthe form of an insert component separate from the turbine casing 14 andarranged at least partially in the installation space 18. Thus, thecover plate 70 acts as wall portion which delimits the nozzle 38 in theaxial direction of the installation space 18 and thus of the turbine 12at the side facing the turbine wheel outlet area 52.

Moreover, as shown in FIG. 1, guide vanes 72 are supported in theturbine casing 14 between the cover plate 70 and the nozzle ring 66 soas to be pivotable about an axis 76, which extends at least essentiallyin the axial direction and thus essentially parallel to the axis ofrotation 22. This allows a variable adjustment of the flow cross-sectionof the nozzle 38, through which the exhaust gas of the combustion engineflows from the spiral duct 16 to the turbine wheel 20. This permits toadjust the turbine 12 to different operating or load points,respectively, of the combustion engine as required, so that the turbine12 and thus the entire exhaust gas turbocharger 10 may be operatedparticularly efficiently.

As can be seen, in particular in conjunction with FIG. 2, the trailingedge 48 of the rotor blade 44 is at least partially, in particularcompletely, covered or overlapped by the cover plate 70. The exhaust gascan therefore mainly, in particular exclusively, flow off the rotorblade 44 across the trailing end 50. This provides for particularlyadvantageous flow conditions for the exhaust gas entering the turbinewheel 20. The cover plate 70 comprises an outer contour 74 around thetrailing edge 48 which at least essentially corresponds to the shape ofthe blade edge 48.

In FIG. 2, the pivot axis 76 can be seen, about which the guide vane 72may be pivoted. The guide vane 72 is supported pivotably about the pivotaxis 76 by the cover plate 70 and the nozzle by bearing journals 78connected to the guide vane. The bearing journals 78 are seated at leastpartially in corresponding seats of the cover plate 70 and the nozzlering 66.

As shown in particular in FIG. 2, the cover plate 70 comprises, in theradial direction of the turbine 12 starting from the axis of rotation22, a first wall area 80 as well as a second wall area 82 adjoining thefirst wall area in the radial direction. The first wall area 80 which inthe axial direction at least partially overlaps the guide vane 72 is setback relative to the second wall area 82 which in the axial direction atleast partially overlaps the guide vane 72. In other words, this meansthat the second wall area 82 in the axial direction is closer to theguide vane 72 than the first wall area 80. The first wall area 80extends in the radial inward direction at least essentially to the samelevel as the leading edge 46 of the rotor blade 44. Thereby, the turbine12 exhibits an extremely low hysteresis, in particular when the guidevane 72 is at least partially opened that is in a position which opensthe flow cross-section of the nozzle 38 partially.

The first wall area 80 and the second wall area 82 are joined via athird wall area 84, wherein the third wall area 84 is arranged betweenthe first wall area 80 and the second wall area 82. In a first exemplaryembodiment, the third wall area 84 extends at an angle of essentially90° each between the first wall area 80 and second wall area 82. Thismeans that the first wall area 80, the second wall area 82 and the thirdwall area 84 are arranged and formed at least essentially step-shaped.

FIG. 3 shows an exemplary embodiment of the exhaust gas turbocharger 10different from that of FIGS. 1 and 2, Whereas the third wall area 84according to FIG. 2 extends essentially parallel to the axial direction(direction arrow 56) and includes an angle of essentially 90° with theradial direction (direction arrow 54), the third wall area 84 accordingto FIG. 3 extends obliquely to the axial direction at an angle with theradial direction different from 90°. Likewise, the third wall area 84includes an angle different from 90° both with respect to the first wallarea 80 and the second wall area 82. The third wall area 84 is formedstraight, i. e. not arc-shaped, round or the like.

FIG. 4 shows still another exemplary embodiment of the exhaust gasturbocharger 10 according to FIGS. 1 to 3. As can be seen from FIG. 4,the third wall area 84 is formed at least essentially arc-shaped in theradial direction (direction arrow 54).

The appropriate design of the first wall area 80, the second wall area82 and the third wall area 84 may be adapted to the requirements andparticular applications. In particular, the respective radial extension(length) and/or axial extension (depth of the first wall area 80, thesecond wall area 82 and the third wall area 84) may be appropriatelydimensioned and varied and deviate from the corresponding extensionsshown in FIGS. 2 to 4. also contours of the first wall area 80, thesecond wall area 82 and the third wall area 84 may be provided which aredifferent from those shown in FIGS. 2 to 4.

What is claimed is:
 1. A turbine for an exhaust gas turbocharger of acombustion engine, comprising a turbine casing (14) including aninstallation space (18), a turbine wheel (20) arranged in theinstallation space (18) so as to be rotatable about an axis of rotation(22) at least one inlet flow duct (38) via which exhaust gas of thecombustion engine may be supplied to the turbine wheel (20), a guidevane structure (72) arranged in the inlet flow duct (38) and includingvanes which are pivotably supported relative to the turbine casing (14),the vane structure (72) being delimited in the axial direction of theinstallation space (18) at least partially by at least one wall portion(70) of the turbine (12) which is at least partially overlapping theguide vane structure (72), the wall portion (70) comprising a first wallarea (80) which is arranged adjacent the guide vane (72), and which isset back relative to a second wall area (82) of the wall portion (70)adjoining the first wall area (80).
 2. The turbine according to claim 1,wherein the wall portion (70) with the first wall area (80) and thesecond wall area (82) is arranged at the side of the guide vanestructure (72) facing the turbine wheel outlet area (52) of the turbine(12).
 3. The turbine according to claim 1, wherein the first wall area(80) and the second wall area (82) are joined via a third wall area (84)of the wall portion (70), which is arranged between the first wall area(80) and the second wall area (82), and forms with the first wall area(80) and the second wall area (82) an angle of essentially 90°.
 4. Theturbine according to claim 1, wherein the first wall area (80) and thesecond wall area (82) are joined via a third wall area (84) of the wallportion (70), which extends between the first wall area (80) and thesecond wall area (82), and is essentially arc-shaped.
 5. The turbineaccording to claim 1, wherein the wall portion (70) is in the form of acover plate (70), which is an insert component formed separately fromthe turbine casing (14) and which is at least partially accommodated inthe installation space (18), and which extends at least over part of theblade edges (48) of the turbine wheel (20).
 6. The turbine according toclaim 5, wherein the cover plate (70) has a cover contour (74) which isessentially complementary to the contour of the blade edges (48).
 7. Theturbine according to claim 1, wherein the guide vane structure (72)abuts a retaining component which is formed separately from the turbinecasing (14), in the form of a nozzle ring (66) which is supported in theturbine casing (14).